/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.io;

import java.util.*;

import java.nio.charset.Charset;

import sun.nio.cs.StreamDecoder;

import sun.nio.cs.StreamEncoder;

/**

 * Methods to access the character-based console device, if any, associated

 * with the current Java virtual machine.

 *

 * <p> Whether a virtual machine has a console is dependent upon the

 * underlying platform and also upon the manner in which the virtual

 * machine is invoked.  If the virtual machine is started from an

 * interactive command line without redirecting the standard input and

 * output streams then its console will exist and will typically be

 * connected to the keyboard and display from which the virtual machine

 * was launched.  If the virtual machine is started automatically, for

 * example by a background job scheduler, then it will typically not

 * have a console.

 * <p>

 * If this virtual machine has a console then it is represented by a

 * unique instance of this class which can be obtained by invoking the

 * {@link java.lang.System#console()} method.  If no console device is

 * available then an invocation of that method will return {@code null}.

 * <p>

 * Read and write operations are synchronized to guarantee the atomic

 * completion of critical operations; therefore invoking methods

 * {@link #readLine()}, {@link #readPassword()}, {@link #format format()},

 * {@link #printf printf()} as well as the read, format and write operations

 * on the objects returned by {@link #reader()} and {@link #writer()} may

 * block in multithreaded scenarios.

 * <p>

 * Invoking {@code close()} on the objects returned by the {@link #reader()}

 * and the {@link #writer()} will not close the underlying stream of those

 * objects.

 * <p>

 * The console-read methods return {@code null} when the end of the

 * console input stream is reached, for example by typing control-D on

 * Unix or control-Z on Windows.  Subsequent read operations will succeed

 * if additional characters are later entered on the console's input

 * device.

 * <p>

 * Unless otherwise specified, passing a {@code null} argument to any method

 * in this class will cause a {@link NullPointerException} to be thrown.

 * <p>

 * <b>Security note:</b>

 * If an application needs to read a password or other secure data, it should

 * use {@link #readPassword()} or {@link #readPassword(String, Object...)} and

 * manually zero the returned character array after processing to minimize the

 * lifetime of sensitive data in memory.

 *

 * <blockquote><pre>{@code

 * Console cons;

 * char[] passwd;

 * if ((cons = System.console()) != null &&

 *     (passwd = cons.readPassword("[%s]", "Password:")) != null) {

 *     ...

 *     java.util.Arrays.fill(passwd, ' ');

 * }

 * }</pre></blockquote>

 *

 * @author  Xueming Shen

 * @since   1.6

 */

public final class Console implements Flushable

{

   /**

    * Retrieves the unique {@link java.io.PrintWriter PrintWriter} object

    * associated with this console.

    *

    * @return  The printwriter associated with this console

    */

    public PrintWriter writer() {

        return pw;

    }

   /**

    * Retrieves the unique {@link java.io.Reader Reader} object associated

    * with this console.

    * <p>

    * This method is intended to be used by sophisticated applications, for

    * example, a {@link java.util.Scanner} object which utilizes the rich

    * parsing/scanning functionality provided by the {@code Scanner}:

    * <blockquote><pre>

    * Console con = System.console();

    * if (con != null) {

    *     Scanner sc = new Scanner(con.reader());

    *     ...

    * }

    * </pre></blockquote>

    * <p>

    * For simple applications requiring only line-oriented reading, use

    * {@link #readLine}.

    * <p>

    * The bulk read operations {@link java.io.Reader#read(char[]) read(char[]) },

    * {@link java.io.Reader#read(char[], int, int) read(char[], int, int) } and

    * {@link java.io.Reader#read(java.nio.CharBuffer) read(java.nio.CharBuffer)}

    * on the returned object will not read in characters beyond the line

    * bound for each invocation, even if the destination buffer has space for

    * more characters. The {@code Reader}'s {@code read} methods may block if a

    * line bound has not been entered or reached on the console's input device.

    * A line bound is considered to be any one of a line feed ({@code '\n'}),

    * a carriage return ({@code '\r'}), a carriage return followed immediately

    * by a linefeed, or an end of stream.

    *

    * @return  The reader associated with this console

    */

    public Reader reader() {

        return reader;

    }

   /**

    * Writes a formatted string to this console's output stream using

    * the specified format string and arguments.

    *

    * @param  fmt

    *         A format string as described in <a

    *         href="../util/Formatter.html#syntax">Format string syntax</a>

    *

    * @param  args

    *         Arguments referenced by the format specifiers in the format

    *         string.  If there are more arguments than format specifiers, the

    *         extra arguments are ignored.  The number of arguments is

    *         variable and may be zero.  The maximum number of arguments is

    *         limited by the maximum dimension of a Java array as defined by

    *         <cite>The Java&trade; Virtual Machine Specification</cite>.

    *         The behaviour on a

    *         {@code null} argument depends on the <a

    *         href="../util/Formatter.html#syntax">conversion</a>.

    *

    * @throws  IllegalFormatException

    *          If a format string contains an illegal syntax, a format

    *          specifier that is incompatible with the given arguments,

    *          insufficient arguments given the format string, or other

    *          illegal conditions.  For specification of all possible

    *          formatting errors, see the <a

    *          href="../util/Formatter.html#detail">Details</a> section

    *          of the formatter class specification.

    *

    * @return  This console

    */

    public Console format(String fmt, Object ...args) {

        formatter.format(fmt, args).flush();

        return this;

    }

   /**

    * A convenience method to write a formatted string to this console's

    * output stream using the specified format string and arguments.

    *

    * <p> An invocation of this method of the form

    * {@code con.printf(format, args)} behaves in exactly the same way

    * as the invocation of

    * <pre>con.format(format, args)</pre>.

    *

    * @param  format

    *         A format string as described in <a

    *         href="../util/Formatter.html#syntax">Format string syntax</a>.

    *

    * @param  args

    *         Arguments referenced by the format specifiers in the format

    *         string.  If there are more arguments than format specifiers, the

    *         extra arguments are ignored.  The number of arguments is

    *         variable and may be zero.  The maximum number of arguments is

    *         limited by the maximum dimension of a Java array as defined by

    *         <cite>The Java&trade; Virtual Machine Specification</cite>.

    *         The behaviour on a

    *         {@code null} argument depends on the <a

    *         href="../util/Formatter.html#syntax">conversion</a>.

    *

    * @throws  IllegalFormatException

    *          If a format string contains an illegal syntax, a format

    *          specifier that is incompatible with the given arguments,

    *          insufficient arguments given the format string, or other

    *          illegal conditions.  For specification of all possible

    *          formatting errors, see the <a

    *          href="../util/Formatter.html#detail">Details</a> section of the

    *          formatter class specification.

    *

    * @return  This console

    */

    public Console printf(String format, Object ... args) {

        return format(format, args);

    }

   /**

    * Provides a formatted prompt, then reads a single line of text from the

    * console.

    *

    * @param  fmt

    *         A format string as described in <a

    *         href="../util/Formatter.html#syntax">Format string syntax</a>.

    *

    * @param  args

    *         Arguments referenced by the format specifiers in the format

    *         string.  If there are more arguments than format specifiers, the

    *         extra arguments are ignored.  The maximum number of arguments is

    *         limited by the maximum dimension of a Java array as defined by

    *         <cite>The Java&trade; Virtual Machine Specification</cite>.

    *

    * @throws  IllegalFormatException

    *          If a format string contains an illegal syntax, a format

    *          specifier that is incompatible with the given arguments,

    *          insufficient arguments given the format string, or other

    *          illegal conditions.  For specification of all possible

    *          formatting errors, see the <a

    *          href="../util/Formatter.html#detail">Details</a> section

    *          of the formatter class specification.

    *

    * @throws IOError

    *         If an I/O error occurs.

    *

    * @return  A string containing the line read from the console, not

    *          including any line-termination characters, or {@code null}

    *          if an end of stream has been reached.

    */

    public String readLine(String fmt, Object ... args) {

        String line = null;

        synchronized (writeLock) {

            synchronized(readLock) {

                if (fmt.length() != 0)

                    pw.format(fmt, args);

                try {

                    char[] ca = readline(false);

                    if (ca != null)

                        line = new String(ca);

                } catch (IOException x) {

                    throw new IOError(x);

                }

            }

        }

        return line;

    }

   /**

    * Reads a single line of text from the console.

    *

    * @throws IOError

    *         If an I/O error occurs.

    *

    * @return  A string containing the line read from the console, not

    *          including any line-termination characters, or {@code null}

    *          if an end of stream has been reached.

    */

    public String readLine() {

        return readLine("");

    }

   /**

    * Provides a formatted prompt, then reads a password or passphrase from

    * the console with echoing disabled.

    *

    * @param  fmt

    *         A format string as described in <a

    *         href="../util/Formatter.html#syntax">Format string syntax</a>

    *         for the prompt text.

    *

    * @param  args

    *         Arguments referenced by the format specifiers in the format

    *         string.  If there are more arguments than format specifiers, the

    *         extra arguments are ignored.  The maximum number of arguments is

    *         limited by the maximum dimension of a Java array as defined by

    *         <cite>The Java&trade; Virtual Machine Specification</cite>.

    *

    * @throws  IllegalFormatException

    *          If a format string contains an illegal syntax, a format

    *          specifier that is incompatible with the given arguments,

    *          insufficient arguments given the format string, or other

    *          illegal conditions.  For specification of all possible

    *          formatting errors, see the <a

    *          href="../util/Formatter.html#detail">Details</a>

    *          section of the formatter class specification.

    *

    * @throws IOError

    *         If an I/O error occurs.

    *

    * @return  A character array containing the password or passphrase read

    *          from the console, not including any line-termination characters,

    *          or {@code null} if an end of stream has been reached.

    */

    public char[] readPassword(String fmt, Object ... args) {

        char[] passwd = null;

        synchronized (writeLock) {

            synchronized(readLock) {

                installShutdownHook();

                try {

                    restoreEcho = echo(false);

                } catch (IOException x) {

                    throw new IOError(x);

                }

                IOError ioe = null;

                try {

                    if (fmt.length() != 0)

                        pw.format(fmt, args);

                    passwd = readline(true);

                } catch (IOException x) {

                    ioe = new IOError(x);

                } finally {

                    try {

                        if (restoreEcho)

                            restoreEcho = echo(true);

                    } catch (IOException x) {

                        if (ioe == null)

                            ioe = new IOError(x);

                        else

                            ioe.addSuppressed(x);

                    }

                    if (ioe != null)

                        throw ioe;

                }

                pw.println();

            }

        }

        return passwd;

    }

    private void installShutdownHook() {

        if (shutdownHookInstalled)

            return;

        try {

            // Add a shutdown hook to restore console's echo state should

            // it be necessary.

            SharedSecrets.getJavaLangAccess()

                .registerShutdownHook(0 /* shutdown hook invocation order */,

                    false /* only register if shutdown is not in progress */,

                    new Runnable() {

                        public void run() {

                            try {

                                if (restoreEcho) {

                                    echo(true);

                                }

                            } catch (IOException x) { }

                        }

                    });

        } catch (IllegalStateException e) {

            // shutdown is already in progress and readPassword is first used

            // by a shutdown hook

        }

        shutdownHookInstalled = true;

    }

   /**

    * Reads a password or passphrase from the console with echoing disabled

    *

    * @throws IOError

    *         If an I/O error occurs.

    *

    * @return  A character array containing the password or passphrase read

    *          from the console, not including any line-termination characters,

    *          or {@code null} if an end of stream has been reached.

    */

    public char[] readPassword() {

        return readPassword("");

    }

    /**

     * Flushes the console and forces any buffered output to be written

     * immediately .

     */

    public void flush() {

        pw.flush();

    }

    private Object readLock;

    private Object writeLock;

    private Reader reader;

    private Writer out;

    private PrintWriter pw;

    private Formatter formatter;

    private Charset cs;

    private char[] rcb;

    private boolean restoreEcho;

    private boolean shutdownHookInstalled;

    private static native String encoding();

    /*

     * Sets the console echo status to {@code on} and returns the previous

     * console on/off status.

     * @param on    the echo status to set to. {@code true} for echo on and

     *              {@code false} for echo off

     * @return true if the previous console echo status is on

     */

    private static native boolean echo(boolean on) throws IOException;

    private char[] readline(boolean zeroOut) throws IOException {

        int len = reader.read(rcb, 0, rcb.length);

        if (len < 0)

            return null;  //EOL

        if (rcb[len-1] == '\r')

            len--;        //remove CR at end;

        else if (rcb[len-1] == '\n') {

            len--;        //remove LF at end;

            if (len > 0 && rcb[len-1] == '\r')

                len--;    //remove the CR, if there is one

        }

        char[] b = new char[len];

        if (len > 0) {

            System.arraycopy(rcb, 0, b, 0, len);

            if (zeroOut) {

                Arrays.fill(rcb, 0, len, ' ');

            }

        }

        return b;

    }

    private char[] grow() {

        assert Thread.holdsLock(readLock);

        char[] t = new char[rcb.length * 2];

        System.arraycopy(rcb, 0, t, 0, rcb.length);

        rcb = t;

        return rcb;

    }

    class LineReader extends Reader {

        private Reader in;

        private char[] cb;

        private int nChars, nextChar;

        boolean leftoverLF;

        LineReader(Reader in) {

            this.in = in;

            cb = new char[1024];

            nextChar = nChars = 0;

            leftoverLF = false;

        }

        public void close () {}

        public boolean ready() throws IOException {

            //in.ready synchronizes on readLock already

            return in.ready();

        }

        public int read(char cbuf[], int offset, int length)

            throws IOException

        {

            int off = offset;

            int end = offset + length;

            if (offset < 0 || offset > cbuf.length || length < 0 ||

                end < 0 || end > cbuf.length) {

                throw new IndexOutOfBoundsException();

            }

            synchronized(readLock) {

                boolean eof = false;

                char c = 0;

                for (;;) {

                    if (nextChar >= nChars) {   //fill

                        int n = 0;

                        do {

                            n = in.read(cb, 0, cb.length);

                        } while (n == 0);

                        if (n > 0) {

                            nChars = n;

                            nextChar = 0;

                            if (n < cb.length &&

                                cb[n-1] != '\n' && cb[n-1] != '\r') {

                                /*

                                 * we're in canonical mode so each "fill" should

                                 * come back with an eol. if there no lf or nl at

                                 * the end of returned bytes we reached an eof.

                                 */

                                eof = true;

                            }

                        } else { /*EOF*/

                            if (off - offset == 0)

                                return -1;

                            return off - offset;

                        }

                    }

                    if (leftoverLF && cbuf == rcb && cb[nextChar] == '\n') {

                        /*

                         * if invoked by our readline, skip the leftover, otherwise

                         * return the LF.

                         */

                        nextChar++;

                    }

                    leftoverLF = false;

                    while (nextChar < nChars) {

                        c = cbuf[off++] = cb[nextChar];

                        cb[nextChar++] = 0;

                        if (c == '\n') {

                            return off - offset;

                        } else if (c == '\r') {

                            if (off == end) {

                                /* no space left even the next is LF, so return

                                 * whatever we have if the invoker is not our

                                 * readLine()

                                 */

                                if (cbuf == rcb) {

                                    cbuf = grow();

                                    end = cbuf.length;

                                } else {

                                    leftoverLF = true;